Cemented tantalum carbide



Patented Sept. 26, 1933 UNITED STATES 1,928,453 CEBIENTED TANTALUM CARBIDE Floyd Kelley,

Schenectady, N. Y., assignor to General Electric Company, a corporation of New York No Drawing. Application November 1, 1930 Serial N 492,872

3 Claims.

The present invention relates to sintered metal compositions generally known as cemented carbides. A composition of this general character is disclosed in Schroter reissue Patent No. 17,624 and consists of a carbide of an element of the sixth group of Mendelejefis table of elements of the periodic system, for example tungsten carbide, and a metal of the iron group, for example cobalt, the latter constituting from about 3% to about 20% of the composition and acting as a cementing or binder medium for tungsten carbide particles in the composition.

' It is one of the objects of the present invention to provide a hard, tough, cemented carbide cutting tool which may be shaped or ground easily and supplied with a keen cutting edge by means of ordinary emery grinding wheels. Other objects of the invention'will appear hereinafter.

The present description will be limited to specific elements, a particular composition, and to details of procedure but with the understanding that any of these may be varied so long as the same or approximately the same results are attained.

In carrying out the invention, I employ tantalum carbide as the main constituent of the cemented carbide, the binder or cementing medium consisting of cobalt and aluminum. In my copending application Serial No. 478,557, filed August 28, 1930, and of which the present application is a continuation-in-part, I have disclosed a composition consisting of tantalum carbide and a metal of the iron group. Although cobalt may be employed alone as a binder element for tantalum carbide, I have found that when the cobalt is mixed with an appreciable quantity of another metal, for example aluminum, and the mixture of cobalt and aluminum employed as a binder for tantalum carbide, the physical qualities of the composition may be considerably improved.

The tantalum carbide is prepared by adding about 12 grams of carbon, for example gas coke, to about 181.5 grams of tantalum, and milling the tantalum and carbon together for about five hours. The milling produces a very intimate mixture of the materials which are then fired at a temperature varying from about 1550 to 1600 C. for about eight hours in a closed graphite tube and in hydrogen furnace. A similar carburizing process is disclosed in my copending application Serial No. 308,565, filed September 26, 1928.

The carbide thus formed is golden brown in color and is milled to break it up into a fine powder capable of passing through a 250 mesh screen. It is then mixed with a suitable quantity pt binder material, for fol a mixture of cobalt example with about 13% and aluminum the binder consisting of about 00 parts by weight of cobalt tion, in order to secure a good joint between the shank and the bit.

Cemented tantalum carbide having the above composition has a hardness of about 81 on the Rockwell A scale and a modulus of rupture of about 120,000 pounds per square inch, the latter figure being obtained on a tool bit as fired and without previous lapping.

Special grinding wheels, such as carborundum wheels are not required to shape the tantalum carbide, since the latter may be shaped easily and quickly by grinding on an ordinary emery wheel. The cemented carbide may be given a very keen cutting edge which it is able to retain under severe operating conditions.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. A hard, tough, sintered composition consisting substantially of tantalum carbide and a binder material for said carbide, said binder material comprising from about 3% to about 20% of said composition, said binder consisting substantially of metal of the iron group and aluminum the aluminum comprising an appreciable quantity but not more than about 10% of said binder.

-2. .A hard, tough, metal composition consisting substantially of tantalum carbide and a cementing medium therefor, said cementing medium comprising from about 3% to about 20% of said composition and consisting of about 90 parts by weight of cobalt and about 10 parts by weight of aluminum.

3. ,A hard, tough, sintered composition consisting substantially of tantalum carbide and a binder material for said carbide, said binder material comprising from about 3% to about 20% of said composition, said binder consisting substantially of about 90 parts by weight of metal of the iron group and about 10 parts by weight of aluminum.

FLOYD C. KELLEY. 

